Factors associated with vaginal detection of prostate-specific antigen among participants in a clinical trial in Malawi.

Self-report of sexual behaviours in clinical studies is often subject to misreporting due to recall or social desirability bias or misinterpretation of the study questionnaires.1 Use of biomarkers of semen exposure, such as the detection of prostate-specific antigen (PSA) in vaginal secretions, offers an additional means of assessing sexual behaviours and condom use that is not subject to reporting biases.2 In a secondary analysis of a clinical trial of hormonal contraception in Malawi,3 we examined associations of discordance between PSA detection and self-report of condomless sex over time with participant characteristics using log-binomial regression analyses with generalised estimating equations for repeated measures. All analyses were conducted using SAS V.9.3 (SAS Institute, Cary, North Carolina, USA). Testing …